Powerset of Subset is Closed under Intersection
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Theorem
Let $S$ be a set.
Let $T \subseteq S$ be a subset of $S$.
Let $\powerset S$ denote the power set of $S$.
Then $\powerset T$ is a closed subset of $\powerset S$ under set intersection:
- $\forall A, B \in \powerset T: A \cap B \in \powerset T$
Proof
A direct application of Power Set is Closed under Intersection.
$\blacksquare$
Sources
- 1965: Seth Warner: Modern Algebra ... (previous) ... (next): Chapter $\text {II}$: New Structures from Old: $\S 8$: Compositions Induced on Subsets: Exercise $8.3$